June 2026 - vsnet-grb-info - ooruri.kusastro.kyoto-u.ac.jp

[vsnet-grb-info 42983] GRB 260604C: GRANDMA observations
by GCN Circulars 06 Jun '26

06 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44851 SUBJECT: GRB 260604C: GRANDMA observations DATE: 26/06/06 17:16:35 GMT FROM: antier(a)ijclab.in2p3.fr L. Chen (TSU), N. Sasaki (UEA,LNA), A. Simon (TShNU of Kyiv), S. Antier (IJCLAB), M. Coughlin (UMN) O. Burkhonov (UBAI), S. Ehgamberdiev (UBAI), Y. Rajabov (UBAI), Y. Tillayev (UBAI), R. Inasaridze (AbAO), N. Kochiashvili (AbAO), V. Zhuzhunadze (AbAO), A. Klotz (IRAP), P. Put (NARIT), K. Noysena (NARIT), A. Manasanun (NARIT), M. Freeberg (KNC), E. Elhosseiny (NRIAG), A. Takey (NRIAG), M. Pillas (IAP), W. Corradi (LNA), T. Leandro de Almeida (LNA), I. Abdusamatjan (TNOT) on behalf of GRANDMA: We conducted follow-up observations of GRB 260604C (Fermi Team, GCN Circ. 44822, Gotz et al., GCN Circ. 44823) with GRANDMA from 0.05 h post T0 (MJD 61195.84859954) up to now. To do this, we have collected data from KNC (Hellot et al., GCN 44835), TAROT/TCH, UBAI-NT60, UBAI-AZT22, AbAO-T70, KAO-1.8m, TRT-SRO, OPD-60, TTT and NOWT. GRB 260604C optical afterglow (reported by Lipunov et al., GCN 44827) is detected at several epochs and a subset of the photometry corrected for Galactic extinction is reported in the public site group of the public ACME service Skyportal/ICARE https://skyportal-icare.ijclab.in2p3.fr/source/GCN-260604_202037. To access, one simply needs to create an account using your ORCID id. Our measurements are in agreement with Lipunov et al., GCN 44827; Konno et al., GCN 44828; Zhu et al., GCN 44832, Becerra et al., GCN 44834; GCN 44835; Gompertz et al., 44843,Saccardi et al. 44844. The observations are performed under the P7 campaign of GRANDMA to monitor SVOM alerts and LSST alerts from explosive fast transients filtered by BOOM/Babamul and FINK. GRANDMA is a worldwide telescope network (grandma.ijclab.in2p3.fr) devoted to the observation of transients in the context of multi-messenger astrophysics (Antier et al. 2020 MNRAS 497, 5518). Kilonova-Catcher (KNC) is the citizen science program of GRANDMA (kilonovacatcher.in2p3.fr). Astrophysics Center for Multimessenger studies in Europe is supported Skyportal/ICARE (contact camille.douzet(a)ijclab.in2p3.fr, skyportal.io) View this GCN Circular online at https://gcn.nasa.gov/circulars/44851. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42982] GRB 260604B: SVOM/GRM detection
by GCN Circulars 06 Jun '26

06 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44850 SUBJECT: GRB 260604B: SVOM/GRM detection DATE: 26/06/06 14:28:23 GMT FROM: zhangjinpeng(a)ihep.ac.cn SVOM/GRM team: Jin-Peng Zhang, Chen-Wei Wang, Shi-Jie Zheng, Yue Huang, Shao-Lin Xiong, Shuang-Nan Zhang (IHEP) SVOM/ECLAIRs team: Olivier GODET (IRAP) Report on behalf of the SVOM team: SVOM/GRM detected GRB 260604B during the routine ground search at 2026-06-04T08:45:56.000 (T0), which is also detected by Fermi/GBM (Fermi GBM Team, GCN #44818). With the event-by-event data downloaded through the X-band ground station, the GRM light curve shows that this burst mainly consists of multiple pulses with a T90 of 17 +9/-5 s in the 15-5000 keV band. The SVOM/GRM light curve can be found here: https://www.bursthub.cn//admin/static/svgrb260604B.png In addition, the position of this burst, according to Fermi/GBM localization (RA = 173.4, Dec = -19.9, Fermi GBM Team, GCN #44818), is located at about 82 degrees from the SVOM optical axis, which is outside the ECLAIRs field of view. With this localization, the time-averaged spectrum from T0-15 to T0+25 s is fitted by a power law function. The power law index is -1.67 +0.10/-0.11. The event fluence (10-1000 keV) in this time interval is (3.8 +0.8/-0.8)E-06 erg/cm^2. The Space Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA, China), National Center for Space Studies (CNES, France) and the Chinese Academy of Sciences (CAS, China), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe. GRM is developed by the Institute of High Energy Physics (IHEP) of CAS. The SVOM/GRM point of contact for this burst is: Jin-Peng Zhang (IHEP) (zhangjinpeng(a)ihep.ac.cn) View this GCN Circular online at https://gcn.nasa.gov/circulars/44850. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42981] GRB 260605A: Insight-HXMT/HE detection
by GCN Circulars 06 Jun '26

06 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44849 SUBJECT: GRB 260605A: Insight-HXMT/HE detection DATE: 26/06/06 14:02:12 GMT FROM: xueyuan zao <zaoxueyuan(a)gmail.com> Xue-Yuan Zao, Chen-Wei Wang, Cheng-Kui Li, Shao-Lin Xiong, and Chao Zheng (IHEP) report on behalf of the Insight-HXMT team: At 2026-06-05T01:04:27.850 (T0), Insight-HXMT/HE detected a long burst, GRB 260605A, which is also detected by SVOM/GRM. The Insight-HXMT/HE light curve mainly consists of a single pulse with a duration (T90) of 11.0 +2.5/-1.0 s. The 1s peak rate, measured from T0+1.75 s, is 6386 cnts/sec. Insight-HXMT/HE detected a total of 22324 counts from this burst. The Insight-HXMT /HE light curve can be found here: https://www.bursthub.cn//admin/static/hxmtgrb260605A.png All measurements above are made with the CsI detectors of Insight-HXMT/HE operating in the regular mode with the energy range of about 60-900 keV (deposited energy). Only gamma-rays with energy greater than about 200 keV can penetrate the spacecraft and leave signals in the CsI detectors installed inside of the telescope. Insight-HXMT is the first Chinese space X-ray telescope, which was funded jointly by the China National Space Administration (CNSA) and the Chinese Academy of Sciences (CAS). More information about it could be found at: http://hxmten.ihep.ac.cn/ View this GCN Circular online at https://gcn.nasa.gov/circulars/44849. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42980] GRB260603A: SVOM/ECLAIRs refined analysis
by GCN Circulars 06 Jun '26

06 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44848 SUBJECT: GRB260603A: SVOM/ECLAIRs refined analysis DATE: 26/06/06 09:24:50 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> M. Brunet (IRAP),N. Dagoneau (CEA), Donghua ZHAO, Wenjin Xie (NAOC), Ruizhi Li (YNAO), Ziming Wang (BNU) report on behalf of the SVOM/ECLAIRs team: Using the event-by-event data downloaded through the X-band ground station, we report further analysis of SVOM/ECLAIRs observations of GRB 260603A (SVOM burst-id sb26060303 – GCN 44787, trigger time T0 = 2026-06-03T05:38:16 UTC). The burst that triggered ECLAIRs onboard shows a single peak lightcurve. The burst duration is T90 = 101 +4/-7 s in the 4-120 keV energy band. The time-averaged spectrum from T0-51.0 s to T0+50.7 s in the 5-120 keV energy range is best fitted by a powerlaw model with alpha = -1.75 +0.08/-0.09. With this model, the 4-120 keV fluence is (1.33 +0.11/-0.12)e-6 erg/cm^2 and the 4-120 keV photon flux is 0.47 +0.02/-0.03 ph/cm^2/s. All the quoted errors are at the 68% confidence level. The Space-based multi-band astronomical Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA), French Space Agency (CNES), and the Chinese Academy of Sciences (CAS), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe. ECLAIRs was developed jointly by CNES, CEA-IRFU, CNRS-IRAP, CNRS-APC. The SVOM/ECLAIRs point of contact for this burst is: Marius Brunet (IRAP) (marius.brunet at utoulouse.fr) View this GCN Circular online at https://gcn.nasa.gov/circulars/44848. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42979] EP260605a: Einstein Probe detection of a fast X-ray transient
by GCN Circulars 06 Jun '26

06 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44847 SUBJECT: EP260605a: Einstein Probe detection of a fast X-ray transient DATE: 26/06/06 06:30:27 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> A.Li (BNU), C. Y. Wang (THU), Z.-C. Zou (NJU), X. H. Tang (THU), H. Sun (NAO, CAS) on behalf of the Einstein Probe (EP) team: We report on the detection of a fast X-ray transient by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission, designated EP260605a. The transient was identified during ground-based telemetry analysis. The WXT light curve started at 2026-06-05T09:31:00 (UTC). The WXT position of the source is R.A. = 273.360 deg, DEC = -40.392 deg (J2000) with an uncertainty of 3.2 arcmin in radius (90% C.L. statistical and systematic). The duration of the event is around 500 s. The WXT spectrum can be fitted with an absorbed power-law, with the absorption fixed at the Galactic value of 1.03 x 10^21 cm^-2, and a photon index of 1.76 (-0.58, +0.61). The unabsorbed 0.5-4 keV flux is 4.3 (-1.3, +1.6) x 10^-11 erg/s/cm2. All uncertainties are reported in 90% C.L. We have arranged follow-up observation with the Follow-up X-ray Telescope onboard EP and will update the information upon receiving the data. Launched on January 9, 2024, EP is a space X-ray observatory to monitor the soft X-ray sky with X-ray follow-up capability (Yuan et al. 2022, Handbook of X-ray and Gamma-ray Astrophysics). View this GCN Circular online at https://gcn.nasa.gov/circulars/44847. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42978] EP260603a: COLIBRÍ optical upper limit
by GCN Circulars 06 Jun '26

06 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44846 SUBJECT: EP260603a: COLIBRÍ optical upper limit DATE: 26/06/05 22:08:07 GMT FROM: Rosa Leticia Becerra Godínez at Instituto de Astronomía, UNAM <rbecerra(a)astro.unam.mx> Enrique Moreno Méndez (UNAM), Dalya Akl (NYUAD), Rosa L. Becerra (UNAM), Alan M. Watson (UNAM), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), Edilberto Aguilar-Ruiz (UNAM), Jean-Luc Atteia (IRAP), Camila Angulo (UNAM), Sarah Antier (IJCLAB), Nathaniel R. Butler (ASU), Damien Dornic (CPPM), Jean-Grégoire Ducoin (CPPM), Francis Fortin (IRAP), Leonardo García García (UNAM), Ramandeep Gill (UNAM), Noémie Globus (UNAM), Marion Guelfand (CPPM), Asuka Kuwata (UNAM), Massimiliano Lincetto (CPPM), Nikos Mandarakas (LAM), Diego López-Cámara (UNAM), Francesco Magnani (CPPM), Margarita Pereyra (UNAM), Ny Avo Rakotondrainibe (LAM), Fredd Sánchez Álvarez (UNAM), Benjamin Schneider (LAM) and Antonio de Ugarte Postigo (LAM) report: We imaged the field of the EP260603a (Liang et al., GCN Circ. 44814) using the DDRAGO two-channel wide-field imager on the COLIBRÍ telescope. We observed from 2026-06-04 06:09 to 06:25 UTC (from 12.30 to 12.58 hours after the trigger) and obtained 14 minutes of simultaneous exposure in the r/z filters. The data were reduced, coadded and analysed with the ASU COLIBRÍ pipeline. The photometry was calibrated using nearby stars from the PanSTARRS DR1 catalog, is in the AB system, and is not corrected for Galactic extinction. In the stacked image, we do not detect any new source within the WXT source region (Liang et al., GCN Circ. 44814) down to the following 5-sigma limit: r > 22.5 z > 21.3 We thank the staff of the Observatorio Astronómico Nacional at Sierra de San Pedro Mártir, as well as the technical and engineering teams at CEA, CPPM, IRAP, LAM, OHP, OSU Pytheas, and UNAM. COLIBRÍ is an astronomical observatory developed and operated jointly by France (AMU, CNES and CNRS) and Mexico (UNAM and SECIHTI). It is located at the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir, Baja California, Mexico. View this GCN Circular online at https://gcn.nasa.gov/circulars/44846. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42977] GRB 260604A: Glowbug gamma-ray detection
by GCN Circulars 06 Jun '26

06 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44845 SUBJECT: GRB 260604A: Glowbug gamma-ray detection DATE: 26/06/05 22:03:48 GMT FROM: C.C. Cheung at Naval Research Lab <Teddy.Cheung(a)nrl.navy.mil> C.C. Cheung, R. Woolf, M. Kerr, J.E. Grove (NRL), A. Goldstein (USRA), C.A. Wilson-Hodge, D. Kocevski (MSFC), and M.S. Briggs (UAH) report: The Glowbug gamma-ray telescope [1,2,3], operating on the International Space Station, reports the detection of GRB 260604A, which was also detected by Fermi/GBM (GCN 44812). Using an adaptive window with a resolution of 32-ms, the burst onset is determined to be 2026-06-04 02:24:24.648 with a duration of 4.1 s and a total significance of about 9.8 sigma. The light curve comprises a single peak. Note that data from ~T0-5s to +1s suffered from deadtime in various detectors. The analysis results presented here are preliminary and use a response function that lacks a detailed characterization of the surrounding passive structure of the ISS. Glowbug is a NASA-funded technology demonstrator for sensitive, low-cost gamma-ray transient telescopes developed, built, and operated by the U.S. Naval Research Laboratory (NRL) with support from the University of Alabama in Huntsville, USRA, and NASA MSFC. It was launched on 2023 March 15 aboard the Department of Defense Space Test Program’s STP-H9 to the ISS and operated until 2024 April when it was put in safe storage on orbit. Glowbug was removed from storage and resumed operation on 2025 September 12. [1] Grove, J.E. et al. 2020, Proc. Yamada Conf. LXXI, arXiv:2009.11959 [2] Woolf, R.S. et al. 2022, Proc. SPIE, 12181, id. 121811O [3] Woolf, R.S. et al. 2024, Proc. SPIE, 13151, id. 1315108 Distribution Statement A: Approved for public release. Distribution is unlimited. View this GCN Circular online at https://gcn.nasa.gov/circulars/44845. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42976] GRB 260604C: LCO optical upper limit
by GCN Circulars 06 Jun '26

06 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44844 SUBJECT: GRB 260604C: LCO optical upper limit DATE: 26/06/05 21:22:48 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> A. Saccardi (CEA/Irfu), D. B. Malesani (DAWN/NBI and Radboud), S. Bisero (CEA/Irfu) report on behalf of the SVOM mission team: We observed the field of GRB 260604C (Fermi GBM Team, GCN 44822; Gotz et al., GCN 44823) with the LCO 1m telescope at South African Astronomical Observatory equipped with the Sinistro instrument. Our observation started on 2026-06-05 at 20:08:32 UT (about 1 day after the trigger) and we obtained 3x200 s exposures in the SDSS r filter. In the stacked image we do not detect the optical counterpart (Lipunov et al., GCN 44827; Konno et al., GCN 44828; Zhu et al., GCN 44832, Becerra et al., GCN 44834; Hellot et al., GCN 44835; Gompertz et al., GCN 44837; Gompertz et al., GCN 44843). We measure the following upper limit calibrated against the Pan-STARRS catalog, and not corrected for Galactic extinction: r > 21.8 AB (3-sigma, mid-time 0.997 days after the trigger). This project is funded by the SVOM collaboration. View this GCN Circular online at https://gcn.nasa.gov/circulars/44844. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42975] GRB 260604C: Liverpool Telescope optical detection
by GCN Circulars 05 Jun '26

05 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44843 SUBJECT: GRB 260604C: Liverpool Telescope optical detection DATE: 26/06/05 14:01:06 GMT FROM: Dimple at University of Birmingham <dimplepanchal96(a)gmail.com> B. P. Gompertz (U. Birmingham), D. B. Malesani (DAWN/NBI and Radboud) and Dimple (U. Birmingham) report on behalf of a larger collaboration: We conducted follow-up observations of GRB 260604C (Fermi Team, GCN Circ. 44822, Gotz et al., GCN Circ. 44823) with the IO:O camera on the 2m robotic Liverpool Telescope (LT). Observations began at 00:14:01 UT on 2026-06-05, ~3.92 hr after the burst, and consisted of 5 x 120 s exposures in each of the SDSS r, g, i and z filters. We detect the optical counterpart (Lipunov et al., GCN 44827; Konno et al., GCN 44828; Zhu et al., GCN 44832, Becerra et al., GCN 44834; Hellot et al., GCN 44835; Gompertz et al. 44837) in all the filters, and measure an AB magnitude of r = 18.60 ± 0.05. Magnitudes are calibrated against nearby Pan-STARRS stars and are not corrected for Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/44843. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42974] The EP-WXT trigger 01709267001 is likely a flaring star
by GCN Circulars 05 Jun '26

05 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44842 SUBJECT: The EP-WXT trigger 01709267001 is likely a flaring star DATE: 26/06/05 12:57:39 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> R.-Z. Li (YNAO), X. Tian (GXU), C.-L. Guo and C.-C. Jin (NAOC) on behalf of the Einstein Probe (EP) team: The EP-WXT trigger 01709267001 at the time of 2026-06-05T12:42:11, is likely a stellar flare associated with RX J1431.6+0047 (High Proper Motion Star). The estimated flux of the flare is around 1.8 x 10^(-10) erg/s/cm^2 in 0.5-4.0 keV, corresponding to an X-ray luminosity of around 4.8 x 10^(31) erg/s. Launched on January 9, 2024, EP is a space X-ray observatory to monitor the soft X-ray sky with X-ray follow-up capability (Yuan et al. 2022, Handbook of X-ray and Gamma-ray Astrophysics). View this GCN Circular online at https://gcn.nasa.gov/circulars/44842. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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